Abo Bibliothek: Guest
International Journal of Fluid Mechanics Research

Erscheint 6 Ausgaben pro Jahr

ISSN Druckformat: 2152-5102

ISSN Online: 2152-5110

The Impact Factor measures the average number of citations received in a particular year by papers published in the journal during the two preceding years. 2017 Journal Citation Reports (Clarivate Analytics, 2018) IF: 1.1 To calculate the five year Impact Factor, citations are counted in 2017 to the previous five years and divided by the source items published in the previous five years. 2017 Journal Citation Reports (Clarivate Analytics, 2018) 5-Year IF: 1.3 The Eigenfactor score, developed by Jevin West and Carl Bergstrom at the University of Washington, is a rating of the total importance of a scientific journal. Journals are rated according to the number of incoming citations, with citations from highly ranked journals weighted to make a larger contribution to the eigenfactor than those from poorly ranked journals. Eigenfactor: 0.0002 The Journal Citation Indicator (JCI) is a single measurement of the field-normalized citation impact of journals in the Web of Science Core Collection across disciplines. The key words here are that the metric is normalized and cross-disciplinary. JCI: 0.33 SJR: 0.256 SNIP: 0.49 CiteScore™:: 2.4 H-Index: 23

Indexed in

A Vortex Plate Theory of Hovering Animal Flight

Volumen 38, Ausgabe 4, 2011, pp. 291-311
DOI: 10.1615/InterJFluidMechRes.v38.i4.10
Get accessGet access

ABSTRAKT

A mathematical model of vortex structure generated during animal hovering flight is adopted to determine the induced power requirement. The wake structure is modelled by a series of equispaced rigid rectangular vortex plates, positioned horizontally and moving vertically downwards with identical speeds; each plate is generated during powering of the functionally wing stroke. These plates are assumed to remain undistorted during their motion and act as rigid surfaces. The flow around the far wake is assumed to be identical to that of the flow about an infinite series of parallel vortex plates moving normal to themselves with constant speed. The vortex representation of the wake considered in the current theory allows a considerable loss of momentum to occur. This loss is approximated by Prandlt’s tip theory. The boundary conditions of this disjointed set of vortex plates determine their velocity potential which contribute to the calculation of the induced power requirement. The current theory is based on the assumption that the impulse associated with the vortex plate is adequate to support the animal’s weight for the duration of the wing stroke period. It is determined that the ratio of the initial vortex plate area Ai to wing swept area Ad is equal to the normal spacing parameter f; which can be related to the hovering parameter K by equating the impulse of the vortex sheet to the vortex plate impulse; K depends upon the animal’s morphology and the kinematics characteristic of the wing stroke. The classical model for induced power estimate is the actuator-disk model which renders the advantage of simplicity. This type of modelling does not precisely correspond to actual events that occur in animal flight. However, the current approach accords well with the nature of the wingbeat since it considers the unsteadiness in the wake as an important fluid dynamical characteristic. Induced power in hovering is calculated as the aerodynamic power required to generate the vortex wake system since this wake is primarily the main physical product of hovering action. Specific mean induced power to mean wing tip velocity ratio is determined by solely the normal spacing parameter f for a given wing stroke amplitude. The current theory gives much higher specific induced power estimate than anticipated by classical methods.

Digitales Portal Digitale Bibliothek eBooks Zeitschriften Referenzen und Berichte Forschungssammlungen Preise und Aborichtlinien Begell House Kontakt Language English 中文 Русский Português German French Spain